Revert to by_price index when globally settling

Because all positions will be closed anyway, using which index
doesn't matter in terms of amounts, however, using another index may
change the ID of historical virtual operations, specifically,
`fill_order_operation` -- we usually try to avoid this.

libraries/chain/db_market.cpp

@@ -62,14 +62,14 @@ void database::globally_settle_asset( const asset_object& mia, const price& sett
    const asset_dynamic_data_object& mia_dyn = mia.dynamic_asset_data_id(*this);
    auto original_mia_supply = mia_dyn.current_supply;
 
-   const auto& call_index = get_index_type<call_order_index>().indices().get<by_collateral>();
+   const auto& call_price_index = get_index_type<call_order_index>().indices().get<by_price>();
 
    auto maint_time = get_dynamic_global_properties().next_maintenance_time;
    bool before_core_hardfork_342 = ( maint_time <= HARDFORK_CORE_342_TIME ); // better rounding
 
    // cancel all call orders and accumulate it into collateral_gathered
-   auto call_itr = call_index.lower_bound( price::min( bitasset.options.short_backing_asset, mia.id ) );
-   auto call_end = call_index.upper_bound( price::max( bitasset.options.short_backing_asset, mia.id ) );
+   auto call_itr = call_price_index.lower_bound( price::min( bitasset.options.short_backing_asset, mia.id ) );
+   auto call_end = call_price_index.upper_bound( price::max( bitasset.options.short_backing_asset, mia.id ) );
    asset pays;
    while( call_itr != call_end )
    {
@@ -94,7 +94,7 @@ void database::globally_settle_asset( const asset_object& mia, const price& sett
    }
 
    modify( bitasset, [&mia,original_mia_supply,&collateral_gathered]( asset_bitasset_data_object& obj ){
-           obj.settlement_price = mia.amount(original_mia_supply) / collateral_gathered; //settlement_price;
+           obj.settlement_price = mia.amount(original_mia_supply) / collateral_gathered;
            obj.settlement_fund  = collateral_gathered.amount;
            });